The present invention, in some embodiments thereof, relates to therapy, and more particularly, but not exclusively, to methods and devices for treating respiratory diseases by pulse inhalation of gaseous nitric oxide at concentration of at least 160 ppm or at equivalent load of gaseous nitric oxide.
Nitric oxide (NO) is a small lipophilic signaling molecule with a small stokes radius and a molecular weight of 30 grams/mol that enables it to cross the glycolipid cell plasma membrane into the cytosol readily and rapidly. NO has an unpaired electron available in its outer orbit that characterizes it as a free radical. NO has been shown to play a critical role in various bodily functions, including the vasodilatation of smooth muscle, neurotransmission, regulation of wound healing and immune responses to infections such as caused by bactericidal action directed toward various organisms. NO has been demonstrated to play an important role in wound healing through vasodilatation, angiogenesis, anti-inflammatory and antimicrobial action.
NO is a common air pollutant and is present in concentrations of 150-650 ppm in cigarette smoke and up to 1200 ppm in cigar and pipe smoke. The National Institute for Occupational Safety and Health (OSHA) and the Environmental Protection Agency have given an inhalation threshold limit value (TLV) as a time-weighted average (TWA) of 25 ppm for NO. The TLV-TWA is the concentration to which a person's respiratory system may be exposed continuously throughout a normal work week without adverse effects and, when represented in ppm hours units, is calculated to be 200 ppm hours. This level is a time-weighted average, that is, the average level of NO should be less than 25 ppm; however, brief exposures to higher concentrations are allowed.
NO is produced by the innate immune response in organs and cells exposed to bacterial and viral infections. These include, among others, the nasopharyngeal airway, lungs and circulating neutrophils and macrophages. NO is also a highly reactive microbicidal free radical that possesses antimicrobial activity against broad range of bacteria, parasites, fungi and viruses. The pore diameter in the cell walls of the microorganisms through which the NO molecule must pass to affect these pathogens is approximately five times wider so that there are few barriers to NO cell penetration. NO is therefore an essential part of the innate immune response. In addition, NO is one of the smallest, yet one of the most important, biological signaling molecules in mammals.
Other than being a well-established direct antimicrobial agent, it has been hypothesized that the antimicrobial and cellular messenger regulatory properties of NO, delivered in an exogenous gaseous form, might easily enter the pulmonary milieu and be useful in optimizing the treatment of uncontrolled pulmonary disease with specific actions directed at reducing bacterial burden, reducing inflammation and improving clinical symptoms.
Some respiratory disorders and physiological conditions can be treated by inhalation of gaseous nitric oxide (gNO). The use of gNO by inhalation can prevent, reverse, or limit the progression of disorders such as acute pulmonary vasoconstriction, traumatic injury, aspiration or inhalation injury, fat embolism in the lung, acidosis, inflammation of the lung, adult respiratory distress syndrome, acute pulmonary edema, acute mountain sickness, post cardiac surgery, acute pulmonary hypertension, persistent pulmonary hypertension of a newborn, perinatal aspiration syndrome, haline membrane disease, acute pulmonary thromboembolism, heparin-protamine reactions, sepsis, asthma and status asthmaticus or hypoxia. Inhaled gNO can also be used to treat cystic fibrosis (CF), chronic pulmonary hypertension, bronchopulmonary dysplasia, chronic pulmonary thromboembolism and idiopathic or primary pulmonary hypertension or chronic hypoxia.
From the toxicological aspect, NO has a half-life in the body of less than 6 seconds and a radius of action of approximately 200 microns from its site of origin, beyond which it is inactivated through binding to sulfhydryl groups of cellular thiols or by nitrosylation of the heme moieties of hemoglobin to form methemoglobin (MetHb). MetHb reductase reduces NO to nitrates in the blood serum. Nitrate has been identified as the predominant nitric oxide metabolite excreted in the urine, accounting for more than 70% of the nitric oxide dose inhaled. Nitrate is cleared from the plasma by the kidney at rates approaching the rate of glomerular filtration. Blood levels of MetHb in healthy humans are typically less than 2%.
Potential side effects of high dose NO treatment hence include the binding of NO to hemoglobin and the formation of MetHb, which could lead to decreased oxygen transport, and the capacity of NO to act as a nitrosylating agent on proteins and other cell constituents. Formation of MetHb and increased levels thereof have been observed in previous studies of gNO inhalation by healthy human individuals, wherein inhalation of gNO at 128 ppm for 3 hours and at 512 ppm for 55 minutes has been reported to drive the levels of MetHb over the safe threshold of 5% [Borgese N. et al., J. Clin. Invest., 1987, 80, 1296-1302; Young J. D. et al., Intensive Care Med., 1994, 20, 581-4 and Young J. D. et al., Brit. J. Anaesthesia, 1996, 76, 652-656].
Thus, concerns have been raised regarding the potential use of NO as a therapeutic agent in various clinical scenarios. To date, studies indicate that acute pulmonary injury, pulmonary edema, hemorrhage, changes in surface tension of surfactant, reduced alveolar numbers and airway responsiveness may be caused by high airway levels of NO, NO2 and other oxides of nitrogen [Hurford W., Resp. Care, 2005, 50, 1428-9].
Several animal studies conducted in order to evaluate the safety window for gNO exposure were reported on the Primary Medical Review of NDA 20-845 (INOmax nitric oxide gas). Included in these reports is the study referred to as RDR-0087-DS, wherein groups of 10 rats each were exposed to room air or to 80, 200, 300, 400 or 500 ppm gNO for 6 continuous hours per day for up to 7 days. It is reported that all of the animals died on the first day of exposure to 400 and 500 ppm gNO with MetHb levels of 72.5 and 67 percents respectively. Six of the animals treated with 300 ppm gNO died during the first 1-2 days. All deaths were attributed to methemoglobinemia.
In additional studies, rats were exposed continuously to room air, 40, 80, 160, 200 and 250 ppm gNO for 6 hours/day for 28 days. No deaths occurred at gNO concentrations below 200 ppm.
At present, inhalation of gaseous nitric oxide (gNO) as a selective, short acting vasodilator is approved only at 80 ppm for use in full term infants with hypoxic respiratory failure associated with pulmonary hypertension. However, other studies have shown that at such low concentration of inhaled gNO, treatment of adults' respiratory diseases is limited, and the use of higher doses of gNO for treating various medical conditions by inhalation requires in-depth safety studies in humans.
Miller et. al. reported the effect of 1,600 ppm hours gNO against five planktonic (suspended in a liquid) species of methicillin resistant S. aureous (MRSA). An in vitro biofilm MRSA model was also used to compare gNO to the antibiotic vancomycin as an antibacterial agent. For the biofilm experiment, a drip flow reactor was used to grow a MRSA biofilm which was then exposed for eight hours to Ringers lactate, 200 ppm gNO (1,600 ppm hours), air or vancomycin (100-times MIC level). A reduction in the population of all five MRSA planktonic strains was observed after exposure to 1,600 ppm hours of gNO. In the biofilm experiment gNO was also shown to reduce MRSA.
Additional animal studies have shown that gNO at 160-200 ppm can exert potent antimicrobial effects against a broad range of microbes in vitro, ex vivo and in animal models [Kelly T. J. et al., J. Clin. Invest., 1998, 102, 1200-7; McMullin B. et al., Resp. Care., 2005, 50, 1451-6; Ghaffari A. et al., Nitric Oxide, 2005, 12, 129-40; Ghaffari A. et al., Wound Repair Regen., 2007, 15, 368-77; Miller C. C. et al., J. Cutan. Med. Surg. 2004, 8, 233-8; Miller C. C. et al., Nitric Oxide, 2009, 20, 16-23], further suggesting its use as an antimicrobial agent in appropriate concentrations.
Studies conducted in a rat model of Pseudomonas aeruginosa pneumonia tested the antimicrobial effect of a gNO inhaled delivery regimen of intermittent 30 minute exposures of 160-200 ppm gNO, and revealed that 160 ppm gNO in that regiment is effective to reduce the pulmonary bioburden and leukocyte infiltration [Hergott C. A. et al., Am. J. Resp. Crit. Care Med., 2006, 173, A135]. This treatment was also shown to decrease the clinical symptoms of bovine respiratory disease in cattle [Schaefer A. L. et al., Online J. Vet. Res., 2006, 10, 7-16].
Miller, C. C. et al. [J. Cutan. Med. Surg., 2004, 8(4), 233-8] reported on topical treatment of a subject who had a chronic, non-healing wound and presence of a reoccurring biofilm with gNO at a treatment concentration of 200 ppm for two weeks. Within the first three days of treatment, the subject's biofilm was no longer visibly present and at one week, the wound size was reduced by 42%. The subject's ulcer continued to heal following the cessation of nitric oxide exposure.
WO 2005/110441 teaches a method and a corresponding device for combating microbes and infections by delivering intermittent doses of 160-400 ppm gNO to a mammal for a period of time which cycles between high and low concentration of nitric oxide gas. The regimen involves delivery of 160 ppm gNO for 30 minutes every four hours with 0-20 ppm delivered for the 3.5 hours between the higher concentration deliveries. No experimental data are presented in this publication.
U.S. Pat. No. 7,122,018 teaches topical intermittent exposure to concentration of nitric oxide ranging 160-400 ppm, for treatment of infected wounds and respiratory infections by a regimen of 4-hour sessions interrupted by 1 hour of rest while monitored methemoglobin blood levels.
U.S. Pat. No. 7,520,866 teaches topical exposure of wounds to gNO at a high concentration ranging 160-400 ppm with a regime of two 4-hour sessions, interrupted by 1 hour of rest, wherein after a first treatment period with high concentration of gNO, a second treatment period at a lower concentration of 5-20 ppm may be provided to restore the balance of nitric oxide and induce collagen expression to aid in the closure of the wound.
WO 2013/132503 discloses methods and systems for intermittent delivery of gNO, at a concentration of about 160 ppm, by inhalation, to human subjects, while showing that such an administration do not cause substantial change in various parameters of the subject.
Pulsed delivery of inhaled nitric oxide has been developed, as a mean to, for example, reduce the exposure to, and inhalation of, nitrogen dioxide by patients treated for pulmonary arterial hypertension (PAH) and chronic obstructive pulmonary disease (COPD) by gNO inhalation at concentrations lower than 150 ppm [Channick, R. N., et al., Chest, 1996, 109(6), p. 1545-9; Nyman, G., et al., Vet Anaesth Analg, 2012, 39(5), p. 480-7; Martin A. R. et al., Medical Gas Research, 2014, 4(1)]. Clinical studies conducted over the years [Kitamukai O. et al., Intern Med, 2002, 41(6), p. 429-34; Barst R. J. et al., Pulm Circ, 2012, 2(2), p. 139-47; and 6. Ivy D. D. et al., J Pediatr, 199, 133(3), p. 453-6] determined that pulsed delivery of inhaled NO may minimize NO and nitrogen dioxide expiratory concentrations, may utilize lower concentration of NO, may eliminate the need for scavenging device, and may reduce environmental pollution [Heinonen, E. et al., Int Care Med, 2000, 26, p. 1116-23; Heinonen, E. et al., Vet Anaesth Analg, 2001, 28, p. 3-11; Heinonen, E. et al., British Journal of Anaesthesia, 2002, 88, p. 394-8; Heinonen, E. et al., British Journal of Anaesthesia, 2003, 90(3), p. 338-42].
Various NO inhalation devices and components thereof are presented in, for example, U.S. Pat. Nos. 5,558,083, 5,558,083, 5,558,083, 5,732,693, 5,752,504, 6,125,846, 7,114,510, 8,282,966, 8,291,904, 8,291,904, 8,293,284, 8,431,163, 8,573,209 and 8,573,210; while NO inhalation devices configured for pulse delivery of NO for treatment of pulmonary arterial hypertension (PAH) and chronic obstructive pulmonary disease (COPD) are currently under development by commercial firms and presented in, for example, U.S. Pat. Nos. 6,164,276 and 6,109,260.
Additional background art includes U.S. Pat. Nos. 8,518,457, 8,083,997, 8,079,998, 8,066,904, 8,057,742, 7,531,133, 7,516,742, 6,432,077, 7,516,742 and 7,955,294; U.S. Patent Application Nos. 2011/0262335, 2011/0259325, 2011/0240019, 2011/0220103 and 2010/0331405, 2011/0112468, 2008/0287861, 2008/0193566, 2007/0116785, 2007/0104653, 2007/0088316, 2007/0086954, 2007/0065473, 2007/0014688, 2006/0207594, 2005/0191372 and WO 1995/10315, WO 2008/095312, WO 2006/071957, WO 2006/110923, WO 2006/110923, WO 2007/057763, WO 2007/057763, WO 2000/30659 and EP 0692984; Miller C. C. et al., Antimicrobial Agents And Chemotherapy, 2007, 51(9), 3364-3366; and Miller C. C. et al., [Resp Care, 2008, 53(11), 1530].